Determination of Parasite Fauna on Freshwater Crayfish “Astacus leptodactylus” (Eschscholtz, 1823) In the Arass Dam Reservoir, Northwest of Iran

Abstract

During the research, from date May 24 to June 26 in year 2015, about 140 specimens of freshwater crayfish with scientific name "Astacus leptodactylus" were captured by funnel baited traps from different stations of the lake and transported to laboratory. A total range of 68 freshwater crayfish specimens out of 140 crayfish with Prevalence rate equal to % 48.5 and mean infection intensity of 4.6, were affected by a kind of parasite called, Branchiobdella hexodonta. This parasite was recovered from carapace and gills of the crustacea. The highest number range of parasite (1-23 number) was seen in length range of 10.6-12.6cm and the lowest number range of parasite (1-11number) observed in length range between 12.7 to 14.9cm. Maximum mean intensity (6.3 number) was in length range of 10.6-12.6cm and minimum mean intensity (3.1 number) was between 12.7 to 14.9. Maximum average abundance (3.6 number) was in length range 10.6-12.6, while minimum average abundance (0.88 number), accounted in length range 8.1-10.5cm. prevalence rate (32%) and mean intensity (4.3) in carapace was higher, in comparison to gills, with prevalence and mean intensity of 20.9% and 2.8, respectively. by increasing length size of crayfish, prevalence rate was increased too. It is worthy of mention that, this worm only parasitism freshwater crayfish, and crayfish is specific host for the parasite. Meanwhile, Annelida Branchiobdella hexodonta, which known as crayfish "Branch worm" is reported for the first time from Iran freshwater crayfish. this worm only parasitism freshwater crayfish and is host specific for crayfish. finally, nematode larvae of Rhabdochona sp. and Cystidicola sp. have not parasitic nature and only have a Commensal state or free-living form, and crayfish act as an intermediate host for them.